Adhesive and sealing layers for electrophoretic displays

ABSTRACT

The invention is directed to methods and compositions for improving the adhesion properties and switching performance of an electrophoretic display. The methods and compositions comprise the use of a high dielectric polymer or oligomer and optionally a crosslinking agent.

This application is a continuation-in-part of U.S. application Ser. No.10/651,540, filed Aug. 29, 2003; which claims the benefit of ProvisionalApplication No. 60/408,256, filed Sep. 4, 2002; the entire contents ofboth are incorporated herein by reference.

FIELD OF THE INVENTION

The invention is directed to methods and compositions for improving theadhesion properties and switching performance of electrophoreticdisplays, particularly at low operation voltages.

BACKGROUND OF THE INVENTION

The electrophoretic display (EPD) is a non-emissive device based on theelectrophoresis phenomenon of charged pigment particles suspended in asolvent. It was first proposed in 1969. The display usually comprisestwo plates with electrodes placed opposing each other, separated byspacers. One of the electrodes is usually transparent. Anelectrophoretic fluid composed of a colored solvent with charged pigmentparticles dispersed therein is enclosed between the two plates. When avoltage difference is imposed between the two electrodes, the pigmentparticles migrate to one side or the other causing either the color ofthe pigment particles or the color of the solvent being seen from theviewing side.

There are several different types of EPDs. In the partition type EPD(see M. A. Hopper and V. Novotny, IEEE Trans. Electr. December,26(8):1148–1152 (1979)), there are partitions between the two electrodesfor dividing the space into smaller cells in order to prevent undesiredmovement of particles, such as sedimentation. The microcapsule type EPD(as described in U.S. Pat. Nos. 5,961,804 and 5,930,026) has asubstantially two dimensional arrangement of microcapsules each havingtherein an electrophoretic composition of a dielectric fluid and asuspension of charged pigment particles that visually contrast with thedielectric solvent. Another type of EPD (see U.S. Pat. No. 3,612,758)has electrophoretic cells that are formed from parallel line reservoirs.The channel-like electrophoretic cells are covered with, and inelectrical contact with, transparent conductors. A layer of transparentglass from which side the panel is viewed overlies the transparentconductors.

The latest improvement to EPD technology involves the use of microcuptechnology. The microcup technology is a significant advance in EPDdisplay technology, allowing for roll to roll manufacturing.

Although EPD technology has advanced, its performance, however, can befurther improved. In a co-pending application, U.S. Ser. No. 10/618,257filed on Jul. 10, 2003, the content of which is incorporated herein byreference in its entirety, methods are disclosed for improving displayperformance. However, when a high absorbance dye or pigment isincorporated into the adhesive layer (15) and carbon black in thesealing layer (14), the display is limited to be viewed from the side ofthe second electrode (12 as shown in FIG. 1) because the opaque color ofthe sealing and adhesive layers from the dye and carbon black makesviewing from the side of the first electrode (11 as shown in FIG. 1)difficult.

Another area for improvement in known EPD devices lie in the adhesivescurrently used. Typical examples of the lamination adhesives includeacrylic and rubber types of pressure sensitive adhesives (such asDURO-TAK 80-1105), hot melt adhesives (such as EVA, polyester orpolyamide types), UV adhesives (based on multifunctional acrylates,vinylethers or epoxides) and thermal or moisture cured adhesives (suchas epoxy resins, polyurethanes, vinyl esters or rubbers). Most of theseconventional adhesives exhibit a strong capacitor effect that oftencauses inferior EPD switching performance. The use of a hydrophilicadhesive or addition of a conductive additive in the adhesive mayalleviate the problems associated with the strong capacitor effect.However, these possible remedies may result in setbacks such assensitivity to humidity and undesirable current leakage or shortcircuitry.

SUMMARY OF THE INVENTION

The present invention provides solutions for at least sorme of thedrawbacks discussed above. Specifically, some embodiments of the presentinvention provide EPD devices with improved performance. It has beenfound that certain high dielectric polymers and oligomers are especiallyeffective in improving the adhesion properties and switching performanceof an electrophoretic display. The present invention also describes waysto provide improved adhesives for use with EPD devices or otherdisplays. Although the present invention is discussed in the context ofEPD devices, it should be understood that some features may beapplicable to other display technologies. At least some of these andother objectives described herein will be met by embodiments of thepresent invention.

A first aspect of the invention is directed to the use of a highdielectric polymer or oligomer for improving the adhesion properties andswitching performance of an electrophoretic display.

A second aspect of the invention is directed to a method for improvingadhesion properties and switching performance of an electrophoreticdisplay which method comprises applying an adhesive solution comprisinga high dielectric polymer or oligomer and optionally a crosslinkingagent, to at least one of the components in the display for adhesion.

A third aspect of the invention is directed to an adhesive compositioncomprising a high dielectric polymer or oligomer and optionally acrosslinking agent. The composition may further comprise a catalyst forthe crosslinking reaction.

A fourth aspect of the invention is directed to a method for improvingadhesion properties and switching performance of an electrophoreticdisplay which method comprises sealing the display cells with a sealingcomposition comprising a high dielectric polymer or oligomer andoptionally a crosslinking agent.

A fifth aspect of the invention is directed to a sealing compositioncomprising a high dielectric polymer or oligomer and optionally acrosslinking agent. The composition may further comprise a catalyst forthe crosslinking action.

In one embodiment, the polymers and oligomers of the inventionpreferably have a dielectric constant higher than that of the solventused in the electrophoretic fluid. It is preferably in the range ofabout 3.5–17, more preferably about 6–15. Among them, polyurethanes,polyureas, polycarbonates, polyamides, polyesters, polycaprolactones,polyvinyl alcohols, polyethers, polyvinyl acetate derivatives, polyvinylfluorides, polyvinylidene fluorides, polyvinyl butyrals,polyvinylpyrrolidones, poly(2-ethyl-2-oxazoline)s, high-acid-numberacrylic or methacrylic polymers or copolymers, cellulose derivatives,gum Arabic, alginate, lecithin and polymers derived from amino acids arepreferred. Suitable cellulose derivatives may include, but are notlimited to, hydroxyethyl cellulose, propyl cellulose, cellulose acetatepropionate, cellulose acetate butyrate or the like and the graftcopolymers thereof.

The polymers and oligomers may have functional group(s) for chainextension or crosslinking during or after lamination.

The adhesive and sealing layers prepared from the compositions of theinvention not only have shown good adhesive properties and high filmstrength, they also exhibit unique low temperature flexibility andadjustable mechanical properties under a broad range of environmentalconditions.

Moreover, because of their good adhesion properties to the electrodelayer, the use of a sealing layer prepared from the sealing compositionof the invention eliminates or alleviates the need of a separateadhesive layer for lamination of the electrode layer to the sealedmicrocups. As a result, the total thickness of the insulating layerbetween the electrophoretic fluid and the electrode plate is reducedwhich results in enhanced switching performance even at a reduceddriving voltage.

In addition in some embodiments, because no carbon black or highabsorbance dyes or pigments are needed in the sealing and adhesivelayers, any possible current leakage or short circuit due to the carbonblack or dyes is eliminated. This is an especially advantageous featurefor high-resolution passive and active matrix display applications.Without the carbon black or dyes, the clear sealing layer allows thedisplay to be viewed from either side of the display which results ingreater process latitude.

A sixth aspect of the invention is directed to an electrophoreticdisplay comprising an adhesive layer and/or a sealing layer of theinvention.

It should be understood, of course, that the improvements used hereinmay be adapted for use with microcup technology. Improved EPD technologycan be found in co-pending applications, U.S. Ser. No. 09/518,488 filedon Mar. 3, 2000 (WO 01/67170), U.S. Ser. No. 09/606,654 filed on Jun.28, 2000 (WO 02/01281) and U.S. Ser. No. 09/784,972 filed on Feb. 15,2001 (WO 02/65215), all of which are incorporated herein by reference.Displays prepared from the microcup technology represent a significantadvancement in the field of display technology.

While the methods and compositions of the invention provide significantimprovement in the adhesion properties and display performance, theyalso provide significant improvement in the manufacturing process.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a typically display cell prepared by the microcuptechnology.

DETAILED DESCRIPTION OF THE INVENTION

I. Definitions

Unless defined otherwise in this specification, all technical terms areused herein according to their conventional definitions as they arecommonly used and understood by those of ordinary skill in the art.Tradenames are identified for materials used and their sources are alsogiven.

The term “Dmax” refers to the maximum achievable optical density of thedisplay.

The term “Dmin” refers to the minimum optical density of the displaybackground.

The term “contrast ratio” is defined as the ratio of the % reflectanceof an electrophoretic display at the Dmax state to the % reflectance ofthe display at the Dmin state.

II. Microcup technology

One embodiment of a microcup based display cell is shown in FIG. 1. Thecell (10) is sandwiched between a first electrode layer (11) and asecond electrode layer (12). A primer layer (13) is optionally presentbetween the cell (10) and the second electrode layer (12). The cell (10)is filled with an electrophoretic fluid and sealed with a sealing layer(14). The first electrode layer (11) is laminated onto the sealed cell,optionally with an adhesive layer.

The display panel may be prepared by microembossing or photolithographyas disclosed in WO 01/67170. In the microembossing process, anembossable composition is coated onto the conductor side of the secondelectrode layer (12) and embossed under pressure to produce the microcuparray. To improve the mold release property and the adhesion between thesealed microcups and the electrode layer, the latter may be pretreatedwith a thin primer layer (13) before being coated with the embossablecomposition.

The embossable composition may comprise a thermoplastic, thermoset or aprecursor thereof which may be selected from a group consisting ofmultifunctional acrylates or methacrylates, vinylbezenes, vinylethers,epoxides, oligomers or polymers thereof, and the like. Multifunctionalacrylates and oligomers thereof are the most preferred. A combination ofa multifunctional epoxide and a multifunctional acrylate is also veryuseful to achieve desirable physico-mechanical properties. Acrosslinkable oligomer imparting flexibility, such as urethane acrylateor polyester acrylate, is usually also added to improve the flexureresistance of the embossed microcups. The composition may contain anoligomer, a monomer, additives and optionally also a polymer. The glasstransition temperature (Tg) for the embossable composition usuallyranges from about −70° C. to about 150° C., preferably from about −45°C. to about 50° C.

The microembossing process is typically carried out at a temperaturehigher than the Tg. A heated male mold or a heated housing substrateagainst which the mold presses may be used to control the microembossingtemperature and pressure.

The mold is released during or after the embossable composition ishardened to reveal an array of microcups (10). The hardening of theembossable composition may be accomplished by cooling, solventevaporation, cross-linking by radiation, heat or moisture. If the curingof the embossable composition is accomplished by UV radiation, UV mayradiate onto the embossable composition through the transparentconductor layer. Alternatively, UV lamps may be placed inside the mold.In this case, the mold must be transparent to allow the UV light toradiate through the pre-patterned male mold on to the thermosetprecursor layer.

A thin primer layer (13) is optionally precoated onto the conductorlayer to improve the release properties of the mold. The composition ofthe primer layer may be the same or different from the embossingcomposition.

In general, the dimension of each individual cells may be in the rangeof about 10² to about 10⁶ μm², preferably from about 10³ to about 5×10⁴μm². The depth of the cells is in the range of about 3 to about 100microns, preferably from about 10 to about 50 microns. The ratio betweenthe area of opening to the total area is in the range of about fromabout 0.05 to about 0.95, preferably from about 0.4 to about 0.9. Thewidth of the openings usually is in the range of about from about 15 toabout 500 microns, preferably from about 25 to about 300 microns, fromedge to edge of the openings.

The microcups are filled with an electrophoretic fluid and sealed asdisclosed in WO 01/67170. The sealing of the microcups may beaccomplished in a number of ways. For example, it may be accomplished byovercoating the filled microcups with a sealing composition comprising asolvent and a sealing material selected from the group consisting ofthermoplastic elastomers, polyvalent acrylates or methacrylates,cyanoacrylates, polyvalent vinyls including vinylbenzenes, vinylsilanesand vinylethers, polyvalent epoxides, polyvalent isocyanates, polyvalentallyls and other oligomers or polymers containing crosslinkablefunctional groups. Additives such as polymeric binder or thickener,photoinitiator, catalyst, filler, colorant or surfactant may be added tothe sealing composition to improve the physico-mechanical and opticalproperties of the display. The sealing composition is essentiallyincompatible with the electrophoretic fluid and has a specific gravitylower than that of the electrophoretic fluid. Upon solvent evaporation,the sealing composition forms a conforming seamless seal on top of thefilled microcups. The sealing layer may be further hardened by heat,radiation, e-beam or other curing methods. Sealing with a compositioncomprising a thermoplastic elastomer is particularly preferred. Examplesof thermoplastic elastomers include tri-block or di-block copolymers ofstyrene and isoprene, butadiene or ethylene/butylene, such as theKraton™ D and G series from Kraton Polymer Company. Crystalline rubberssuch as poly(ethylene-co-propylene-co-5-methylene-2-norbornene) andother EPDM (Ethylene Propylene Diene Rubber terpolymer) from Exxon Mobilhave also been found very useful.

Alternatively, the sealing composition may be dispersed into anelectrophoretic fluid and filled into the microcups. The sealingcomposition is essentially incompatible with the electrophoretic fluidand is lighter than the electrophoretic fluid. Upon phase separation andsolvent evaporation, the sealing composition floats to the top of thefilled microcups and forms a seamless sealing layer thereon. The sealinglayer may be further hardened by heat, radiation or other curingmethods.

The sealed microcups finally are laminated with the first electrodelayer (11) optionally pre-coated with an adhesive layer (15).

III. Polymers and Oligomers Useful for the Present Invention

The polymers and oligomers useful for the present invention have adielectric constant higher than that of the dielectric solvent used inthe electrophoretic fluid. However, polymers having a very highdielectric constant tend to be hydrophilic and may result in poorenvironmental stability particularly under high humidity conditions. Foroptimum performance, the dielectric constant of the polymers oroligomers for this invention is preferably in the range of about 3.5–17,more preferably 6–15. Among them, the colorless and transparent polymersare the most preferred.

Examples include polyurethanes, polyureas, polycarbonates, polyamides,polyesters, polycaprolactones, polyvinyl alcohols, polyethers, polyvinylacetate derivatives [such as poly(ethylene-co-vinylacetate)], polyvinylfluorides, polyvinylidene fluorides, polyvinyl butyrals,polyvinylpyrrolidones, poly(2-ethyl-2-oxazoline)s, high-acid-numberacrylic or methacrylic polymers or copolymers, cellulose derivatives,gum Arabic, alginate, lecithin and polymers derived from amino acids.Suitable cellulose derivatives may include, but are not limited to,hydroxyethyl cellulose, propyl cellulose, cellulose acetate propionate,cellulose acetate butyrate or the like and the graft copolymers thereof.The composition of the present invention may comprise one or more of thehigh dielectric polymers or oligomers.

The polymers and oligomers preferably have functional groups for chainextension or crosslinking during or after lamination.

Among the polymers and oligomers mentioned above, polyurethanes,polyureas, polycarbonates, polyesters and polyamides, especially thosehaving functional groups are particularly preferred because of theirsuperior adhesion and optical properties and high environmentalresistance.

Examples for the functional groups include, but are not limited to, —OH,—SH, —NCO, —NCS, —NHR, —NRCONHR, —NRCSNHR, vinyl, epoxide andderivatives thereof, including cyclic derivatives. The “R” mentionedabove may be hydrogen, alkyl, aryl, alkylaryl or arylalkyl of up to 20carbon atoms. The alkyl, aryl, alkylaryl or arylalkyl may alsooptionally comprise N, O, S or halogen. Preferred “R”s may include, butare not limited to, hydrogen, methyl, ethyl, phenyl, hydroxymethyl,hydroxyethyl and hydroxybutyl.

Functionalized polyurethanes, such as hydroxyl terminated polyesterpolyurethanes or polyether polyurethanes, isocyanate terminatedpolyester polyurethanes or polyether polyurethanes, and acrylateterminated polyester polyurethanes, or polyether polynrethanes areparticularly preferred.

The polyester polyols or polyether polyols used for the synthesis ofpolyester polyurethanes or polyether polyurethanes include, but are notlimited to, polycaprolactone, polyesters (derived from, for example,adipic acid, phthalate anhydride or maleic anhydride), polyethyleneglycol and its copolymers and polypropylene glycol and its copolymers.Among the polyester polyurethanes, the hydroxyl terminated polyesterpolyurethanes, such as those from the IROSTIC series (by HuntsmanPolyurethanes) are some of the most preferred. Tables of dielectricconstants of typical commercially available polymers can be found inliterature such as “Electrical Properties of Polymers”, by C. C. Ku andR. Liepins; Hanser Publishers, 1993; and “Prediction of PolymerProperties” 3^(rd). ed., by J. Bicerano; Marcel Dekker, Inc., 2002. Someof them are listed in Table 1 below:

TABLE 1 Dielectric Constants of Polymers (from “Electrical Properties ofPolymers”, by C.C. Ku and R. Liepins, Hanser Publishers, 1993)Temperature Frequency Polymers ε (° C.) (Hz) Polyvinyl alcohol/acetate),0–1.5% 10.4 25  10³ acetate (Elvannol 50A-42) Polyether polyurethane(based on 10 18  10 polyethylene oxide 600) Polyurethane Elastomers 4.7–9.53 25  60 Polyfumaronitrile 8.5 26  10³ Poly (vinyl fluoride) 8.525  10³ Poly (vinylidene fluoride) 8.4 25  10³ Melamine/formaldehyderesin 7.9 25  60 Cellulose nitrate 7.0–7.5 25  60 Polysulfide 7.3 25  60Phenol/aniline/formaldehyde 7.15 24  10³ (Bakelite BT-48-306)Chlorosulfonated polyethylene 7.0 25  60 Melamine/phenol resin 7.0 25 60 Methyl cellulose (Methocel) 6.8 22  10³ Poly (urea/formaldehyde) 6.724  10³ Cellulose acetate butyrate 3.2–6.2 25  10³ Cellulose acetatepropionate 3.2–6.2 25  10⁶ Phenol/aniline/formaldehyde 5.70 24  60(Durite No. 221X) Phenol/aniline/formaldehyde 4.50 25  10³ Cellulosetriacetate 3.2–4.5 25  10³ Epoxy, standard (Bisphenol A) 4.02 25  60Poly(methyl methacrylate)/ 4.0 25  60 polyvinyl chloride)alloy Nylon 664.0 25  60 Nylon 6/12 4.0 25  60 Allyl diglycol carbonate 2.0–3.9 25 10⁴ Acetal(polyoxymethylene), Delrin 3.7 25  60 Nylon 6 3.7 25Aniline-formaldehyde 3.68 25  10³ (Dilectene 100) Aromaticpolyester-imides 3.50 25  10³ Aromatic polyimides 3.5 25  10³Acrylonitril-Butadiene-Styrene 2.5–3.5 25  60 (ABS) Aromaticpolyamideimides 3.32 25  10³ Poly (butadiene) 3.3 25  10⁶ Cellulose,regenerated (cellophane) 3.2 25  10³ Cellulose propionate 3.2 25  10⁶Cycloaliphatic epoxy resin 3.2 25  60 Poly(ethylene terephthalate), 3.225  10³ thermoplastic Poly(butyl terephthalate) 3.2 25 100Ethylene/vinyl acetate copolymer 3.16 25  60 Aromatic polyethers 3.14 25 60 Aromatic polysulfone 3.13 23  10³ Poly (methyl methacrylate), 3.1227  10³ Plexiglas Ethyl cellulose, Ethocel LT-5 3.09 25  10³ Poly (vinylchloride), chlorinated 3.08 25  60 Poly (vinyl acetate) Elvacet 3.07 25 10³ 42A-900) Polysiloxane resin (methyl, 3.04 25  10³ phenyl, andmethylphenyl) Poly(styrene/acrylonitrile) (SAN) 2.6–3.0 25  10⁴Polycarbonate 2.99 25  10³ Methyl and methylphenyl 2.90 20  10³polysiloxane (DC 550) Poly(ethyl methacrylate) 2.75 22  10³ Poly (methylmethacrylate) 2.68 25  10³ Poly(buty methacrylate) 2.62 24 100Poly(2,6-dimethyl-1,4- 2.6 25  10³ phenylene ether) Fluorinatedethylene/propylene 2.0–2.5 25  10³ copolymer (FEP) SBR (75% butadiene)2.5 26  10³ Polystyrene 2.4 25  10³ Poly(98–99% isobutylene/1–2% 2.38 25 10³ isoprene) (GR-I; butyl rubber) Polyethylene, ultra high MW 2.3 25 10³ Polyethylene, medium density 2.2 25  10³ Polytetrafluoroethylene2.0 25  10³IV. The Methods and Compositions of the Invention

The adhesive solution and sealing composition of the invention comprisea high dielectric polymer or oligomer as described above and optionallya crosslinking agent.

Suitable crosslinking agents for hydroxy-terminated or amino-terminatedhigh dielectric polymers include multifunctional isocyanates orisothiocyanates, multifunctional epoxides, polyaziridines, among whichaliphatic polyisocyanates (e.g., Desmodur N-100 from Bayer and IrodurE-358 from Huntsman Polyurethane) and polyaziridine are the mostpreferred.

When a hydroxyl terminated polyester polyurethane is used as the highdielectric polymer and a polyisocyanate is used as the crosslinkingagent in the composition, the molar ratio of the hydroxyl group of thehydroxyl terminated polyester polyurethane to the isocyanate group ofthe polyisocyanate is preferably 1/10 to 10/1, more preferably 1.1/1 to2/1.

While a crosslinking agent is present, a catalyst may also be added topromote the crosslinking reaction. Suitable catalysts include, but arenot limited to, organotin catalysts (e.g., dibutyl tin dilaurate,DBTDL), organozirconium catalysts (e.g., zirconium chelate2,4-pentanedione, K-KAT XC-4205 and K-KAT XC-6212 from King Industry),bismuth catalysts (e.g., K-KAT 348 also from King Industry), withorganotin and organozirconium catalysts being the most preferred.

Suitable crosslinking agents for multifunctional isocyanate-terminatedhigh dielectric polymers include multifunctional alcohols and aminessuch as butanediol, pentanediol, glycerol, triethanolamine,N,N,N′,N′-tetrakis(2-hydroxyethyl)ethylene diamine, ethylene diamine,diethylene triamine, Jeffamine, polyimine and derivatives thereof.

The adhesive solution and sealing composition may be prepared bydissolving or dispersing an appropriate amount of the high dielectricpolymer or oligomer in a solvent or solvent mixture. The concentrationof the polymer or oligomer is preferably in the range of about 20–99.5%by weight, more preferably in the range of about 50–95% by weight.

Suitable solvents include ketones such as methyl ethyl ketone (MEK),methyl isobutyl ketone (MIBK), cyclohexanone or acetone; esters such asbutyl acetate, isopropyl acetate or ethyl acetate; ethers such astetrahydrofuran (THF), 1,2-diethoxy ethane or a mixture thereof.

The solution is subject to thorough mixing followed by degassing beforeuse.

A crosslinking agent and optionally 0.1–1% by weight of a catalyst basedon total solid weight may be added to the adhesive solution or thesealing composition.

In another embodiment, part of the high dielectric polymer or oligomerin the composition may be replaced with a radically or photochemicallygraftable polymer. Suitable graftable polymers may include, but are notlimited to, cellulose derivatives such as cellulose acetate butyrate(CAB), cellulose acetate propionate (CAP), hydroxypropyl cellulose(HPC), hydroxybutyl cellulose (HBC), hydroxyethyl cellulose (HEC),methyl cellulose (MC), carboxymethyl cellulose (CMC) or copolymersthereof and polyvinyl alcohol derivatives such as polyvinyl acetal,polyvinyl butyral or copolymers thereof. Polymers of a high glasstransition temperature (Tg) and high modules at the applicationconditions (temperature, pressure, shear rate etc.) are preferred.Particularly preferred polymers include cellulose acetate, celluloseacetate butyrate, cellulose acetate propionate, polyvinyl acetal andcopolymers thereof.

The radically or photochemically graftable polymer may be about 5% toabout 30% by weight, preferably about 10% to about 20% by weight, of thehigh dielectric polymer or oligomer.

In this case, the composition may comprise a photoinitiator. Suitablephotoinitiators may include, but are not limited to, benzophenone, ITX(isopropyl thioxanthone), BMS (4(p-tolylthio)benzophenone) and others,for example, Irgacure 651 (2,2-dimethoxy-1,2-diphenylethane), 907(2-methyl-1-[4-(methylthio)phenyl]-2-morpholino-1-propanone), 369(2-benzyl-2-(dimethylamino)-1-[4-(4-morpholinyl)phenyl]-1-butanone) or184 (1-hydroxycyclohexylphenylketone) (all from Ciba SpecialtyChemicals). The photoinitiator, if present, is usually in the amount ofabout 0.5% to about 5%, preferably about 1% to about 3% by weight, basedon the total weight of the high dielectric polymer or oligomer and thegraftable polymer.

The graftable polymer containing composition is formed by dissolving thehigh dielectric polymer or oligomer, the graftable polymer and aphotoinitiator, if present, in a solvent system as described above.

If the composition is used as an adhesive, the solution is coated ontothe electrode layer (11 in FIG. 1). The coated electrode layer is thenlaminated over the sealed microcups and the resultant assembly isfinally post cured as described below. In this case, the display cellsare pre-sealed with a conventional sealing layer.

If the composition is used as a sealing composition, the solution iscoated onto microcups pre-filled with an electrophoretic fluid. In thiscase, the sealing layer may also serve as an adhesive layer, which meansthat the electrode layer (11 in FIG. 1) may be pressed directly onto thesealing layer with the ITO side facing the sealing layer, without theneed of a separate adhesive layer.

The post-curing of the assemblies comprising the adhesive or sealinglayer of the invention may be carried out at a temperature in the rangeof about 50–100° C. for about 0.5 to 2 hours followed by additionalheating at 40–80° C. for 6–24 hours to ensure completion of thecrosslinking of the polymers.

V. EXAMPLES

The following examples are given to enable those skilled in the art tomore clearly understand and to practice the present invention. Theyshould not be considered as limiting the scope of the invention, butmerely as being illustrative and representative thereof.

GLOSSARY Acronym Full Name Description HPU-20 IROSTIC P 9820-20 Hydroxylterminated polyester polyurethane, Huntsman Polyurethane, Viscosity1800–2200 mPs at 20° C. HPU-18 IROSTIC P 9820-18 Hydroxyl terminatedpolyester polyurethane, Huntsman Polyurethane, Viscosity 1600–2000 mPsat 20° C. HPU-12 IROSTIC P 9820-12 Hydroxyl terminated polyesterpolyurethane, Huntsman Polyurethane, Viscosity 1000–1400 mPs at 20° C.PSA DURO-TAK 80-1105 Pressure sensitive adhesives, National Starch andChemical Company IE-359 IRODUR E 359 polyisocyanate, 20% of ethylacetate solution, NCO content: 6.1%, Huntsman Polyurethane, DN-100DESMODUR N-100 HDI, aliphatic poly triisocyanate, NCO content: 22.1–22%Bayer. KK-348 K-KAT348 Bismium carboxylate 2-ethylhexane acid, KingIndustry KFG190x Kraton ™ FG190x Thermoplastic rubber containing maleicanhydride functionalized triblock copolymer consisting of polystyreneend blocks and poly ethylene/butylene middle blocks. Shell ElastomerLLC. KG1650 Kraton ™ G1650 Thermoplastic rubber containing triblockcopolymer consisting of polystyrene end blocks and polyethylene/butylene middle blocks. Shell Elastomer LLC. KRPG6919 Kraton ™RPG6919 Thermoplastic rubber containing hydrogenated (branchpolyisoprene chains) block copolymer consisting of polystyrene endblocks and poly ethylene/butylenes middle blocks. Shell Elastomer LLC.AP LHT-240 Arcol Polyol LHT-240i Tri-functional polyether polyols, BayerDBTDL Dibutyltin Dilaurate Tin catalyst, Aldrich DZ4470 Desmodur Z4470Di-functional aliphatic polyisocyanate, Bayer VXC72 Vulcan ™ XC72Conductive carbon black particles (particle size ~30 nm) from CabotCorp., SL7500 Silwet L7500 Polyalkyleneoxide modifiedpolydimethylsiloxane. wetting agents, OSI specialties. BYK142 Carbonblack dispersion agents, BYK-Chemie CAPA 6806 CAPA 6806 Hydroxylterminated polycaprolactones, Tri-Iso Company Isopar E Isopar E Solvent,ExxonMobil

17.8 Gm of KRYTOX® methyl ester (DuPont, MW=about 1780, g=about 10) wasdissolved in a solvent mixture containing 12 gm of1,1,2-trichlorotrifluoroethane (Aldrich) and 1.5 gm ofα,α,α-trifluorotoluene (Aldrich). The resultant solution was added dropby drop into a solution containing 7.3 gm of tris(2-aminoethyl)amine(Aldrich) in 25 gm of α,α,α-trifluorotoluene and 30 gm of1,1,2-trichlorotrifluoroethane over 2 hours with stirring at roomtemperature. The mixture was then stirred for another 8 hours to allowthe reaction to complete. The IR spectrum of the crude product clearlyindicated the disappearance of C═O vibration for methyl ester at 1780cm⁻¹ and the appearance of C═O vibration for the amide product at 1695cm⁻¹. Solvents were removed by rotary evaporation followed by vacuumstripping at 100° C. for 4–6 hours. The crude product was then dissolvedin 50 ml of PFS2 solvent (perfluoropolyether from Solvay Solexis) andextracted with 20 ml of ethyl acetate three times, then dried to yield17 gm of purified product (R_(f)-amine1900) which showed excellentsolubility in HT200.

Other reactive R_(f) amines having different molecular weights such asR_(f)-amine4900 (g=about 30), R_(f)-amine2000 (g=about 11),R_(f)-amine800 (g=about 4) and R_(f)-amine650 (g=about 3) were alsosynthesized according to the same procedure.

Preparation 2 Preparation of TiO₂-Containing Microcapsules as theElectrophoretic Fluid

9.05 Gm of DESMODUR® N3400 aliphatic polyisocyanate (from Bayer AG) and0.49 gm of triethanolamine (99%, Dow) were dissolved in 3.79 gm of MEK.To the resultant solution, 13 gm of TiO₂ R706 (DuPont) was added andhomogenized for 2 minutes with a rotor-stator homogenizer (IKAULTRA-TURRAX T25, IKA WORKS) at ambient temperature. A solutioncontaining 1.67 gm of 1,5-pentanediol (BASF), 1.35 gm of polypropyleneoxide (mw=725 from Aldrich), 2.47 gm of MEK and 0.32 gm of a 2%dibutyltin dilaurate (Aldrich) solution in MEK was added and furtherhomogenized for 2 minutes. In the final step, 0.9 gm of R_(f)-amine 4900from Preparation 1 in 40.0 gm of HT-200 (Solvay Solexis) was added andhomogenized for 2 minutes, followed by addition of additional 0.9 gm ofR_(f)-amine 4900 in 33.0 gm of HT-200 and homogenization for 2 minutes.A microcapsule dispersion with low viscosity was obtained. Themicrocapsule dispersion obtained was heated at 80° C. overnight andstirred under low shear to post-cure the particles. The resultantmicrocapsule dispersion was filtered through a 400-mesh (38 micrometer)screen and the solid content of the filtered dispersion was measured tobe 29% by weight with an IR-200 Moisture Analyzer (Denver InstrumentCompany).

The average particle size of the filtered dispersion was measured withthe Beckman Coulter LS230 Particle Analyzer to be about 2 μm.

An EPD fluid containing 1.3% by weight of CuPc-C₈F₁₇ (structure givenbelow) and 6% by weight (dry weight) of the resultant TiO₂ microcapsulein HT-200 was filled into the microcups which were then sealed andsandwiched between two ITO/PET films according to the proceduredescribed in Preparation 3.

Preparation 3A Primer Coated Transparent Conductor Film

A primer coating solution containing 33.2 gm of EB 600™ (acrylated epoxyoligomer, UCB, Smyrna, Ga.), 16.12 gm of SR 399™ (pentafunctionalmonomer, Sartomer, Exton, Pa.), 16.12 gm of TMPTA (UCB, Smyrna, Ga.),20.61 gm of HDODA (1,6-hexanediol diacrylate, UCB, Smyrna, Ga.), 2 gm ofIrgacure™ 369(2-benzyl-2-(dimethylamino)-1-[4-(4-morpholinyl)phenyl]-1-butanone,Ciba, Tarrytown, N.Y.), 0.1 gm of Irganox™ 1035 (thiodiethylenebis(3,5-di(tert)-butyl-4-hydroxyhydrocinnamate, Ciba), 44.35 gm ofpoly(ethyl methacrylate) (MW. 515,000, Aldrich, Milwaukee, Wis.) and399.15 gm of MEK (methyl ethyl ketone) was mixed thoroughly and coatedonto a 5 mil transparent conductor film (ITO/PET film, 5 mil OC50 fromCPFilms, Martinsville, Va.) using a #4 drawdown bar. The coated ITO filmwas dried in an oven at 65° C. for 10 minutes, then exposed to 1.8 J/cm²of UV light under nitrogen using a UV conveyer (DDU, Los Angles,Calif.).

Preparation 3B Preparation of Microcups

Microcup Composition Component Weight Part Source EB 600 33.15 UCB SR399 32.24 Sartomer HDDA 20.61 UCB EB1360 6.00 UCB Hycar X43 8.00 BFGoodrich Irgacure 369 0.20 Ciba ITX 0.04 Aldrich Antioxidant Ir1035 0.10Ciba

33.15 Gm of EB 600™ (UCB, Smyrna, Ga.), 32.24 gm of SR 399™ (Sartomer,Exton, Pa.), 6 gm of EB1360™ (silicone acrylate, UCB, Smyrna, Ga.), 8 gmof Hycar 1300×43 (reactive liquid polymer, Noveon Inc. Cleveland, Ohio),0.2 gm of Irgacure™ 369 (Ciba, Tarrytown, N.Y.), 0.04 gm of ITX(Isopropyl-9H-thioxanthen-9-one, Aldrich, Milwaukee, Wis.), 0.1 gm ofIrganox™ 1035 (Ciba, Tarrytown, N.Y.) and 20.61 gm of HDDA(1,6-hexanediol diacrylate, UCB, Smyrna, Ga.) were mixed thoroughly witha Stir-Pak mixer (Cole Parmer, Vernon, Ill.) at room temperature forabout 1 hour and debubbled by a centrifuge at 2000 rpm for about 15minutes.

The microcup composition was slowly coated onto a 4″×4″ electroformed Nimale mold for an array of 72 μm (length)×72 μm (width)×35 μm (depth)×13μm (width of top surface of the partition wall between cups) microcups.A plastic blade was used to remove excess of fluid and gently squeeze itinto “valleys” of the Ni mold. The coated Ni mold was heated in an ovenat 65° C. for 5 minutes and laminated with the primer coated ITO/PETfilm prepared in Preparation 3A, with the primer layer facing the Nimold using a GBC Eagle 35 laminator (GBC, Northbrook, Ill.) preset at aroller temperature of 100° C., lamination speed of 1 ft/min and the rollgap at “heavy gauge”. A UV curing station with a UV intensity of 2.5mJ/cm² was used to cure the panel for 5 seconds. The ITO/PET film wasthen peeled away from the Ni mold at a peeling angle of about 30 degreeto give a 4″×4″ microcup array on ITO/PET. An acceptable release of themicrocup array from the mold was observed. The thus obtained microcuparray was further post-cured with a UV conveyor curing system (DDU, LosAngles, Calif.) with a UV dosage of 1.7 J/cm².

Preparation 3C Filling and Sealing with a Sealing Composition

1 Gm of an electrophoretic fluid containing 6% by weight (dry weight) ofthe TiO₂ microcapsules prepared according to Preparation 2 and 1.3% byweight of a perfluorinated Cu-phthalocyanine dye (CuPc-C₈F₁₇) in HT-200(Solvay Solexis) was filled into the 4″×4″ microcup array prepared fromPreparation 3B using a #0 drawdown bar. The excess of fluid was scrapedaway by a rubber blade.

A sealing composition was then overcoated onto the filled microcupsusing a Universal Blade Applicator and dried at room temperature to forma seamless sealing layer of about 2–3 μm dry thickness with gooduniformity. The sealing solution used is indicated in each examplebelow.

Preparation 3D Lamination of Electrode Layer

An adhesive solution was first coated onto the ITO side of a 5-milITO/PET film. The adhesive composition used is indicated in each examplebelow. The coated film was then laminated over the sealed microcups by alaminator at 100° C. at a linear speed of 20 cm/min.

Alternatively, when the display cells are sealed with a sealingcomposition of the invention, the electrode layer may be laminateddirectly over the sealed microcups without a separate adhesive layer.

Examples 1–5 Microcup EPDs with both Sealing and Adhesive Layers

Examples 1–5 demonstrate the adhesive layer of the present invention.All five examples used the same sealing composition which was preparedby dissolving 0.48 parts (by weight) of Kraton™ FG190x (from Shell,Tex.), 0.91 parts of Kraton™ RPG6919 (from Shell, Tex.), 8.19 parts ofKraton™ G1650 (from Shell Elastomer LLC, TX), 0.043 parts of BYK142(from BYK-Chemie) and 0.18 parts of Silwet L7500 (from OSI Specialties)in 79.9 parts of Isopar E (from ExxonMobil) and 8.88 parts of isopropylacetate (from Aldrich). To the resultant solution, 1.43 parts of carbonblack, Vulcan™ XC72 (from Cabot Crop.), was added to the solution undermixing. Mixing was continued for 45 minutes at 10500 rpm. The finaldispersion was filtered through a 20 μm filter and coated on the filledmicrocups as described in Preparation 3C.

Example 1 Comparative Example, Kraton Elastomer Sealing Layer and PSAAdhesive Layer

The ITO side of an ITO/PET conductor film (5 mil OC50 from CPFilms) wasovercoated with a 14% by weight solution of a pressure sensitiveadhesive (DRUO-TAK 80-1105, from National Starch and Chemical Company)in MEK by a drawdown bar (targeted coverage: 0.3 gM/ft²). The adhesivecoated ITO/PET layer was then laminated over the sealed microcupsprepared from the procedure as described under the heading of Examples1–5 above, with a GBC Eagle 35 laminator at 100° C. The lamination speedwas set at 20 cm/min with a gap of 1/32″. The laminated film was thenbaked in a 65° C. oven for 1 hour to remove the residue solvent.

The contrast ratio as defined above was measured using a GretagMacbeth™Spectrolino spectrometer against a standard black background. Theresults are shown in Table 1.

Example 2 Kraton Elastomer Sealing Layer and PU Adhesive Layer

The same procedure for the preparation of the Comparative Example 1 wasfollowed, except that the pressure sensitive adhesive (DRUO-TAK 80-1105,from National Starch and Chemical Company) was replaced with a 14% (byweight) solution of polyurethane IROSTIC P9820-20 (from HuntsmanPolyurethanes) in MEK/ethyl acetate (at 92.5/7.5 ratio by weight). Thecontrast ratios of the display of Example 2 are shown in Table 1.

Example 3 Kraton Elastomer Sealing Layer and PU Adhesive Layer

The same composition and procedure for the preparation of Example 2 werefollowed, except that the 14% (by weight) solution of IROSTIC P9820-20(from Huntsman) was replaced with a 14% (by weight) solution of IROSTICP9820-18 (from Huntsman Polyurethanes). The contrast ratios of thedisplay of Example 3 are also shown in Table 1.

Example 4 Kraton Elastomer Sealing Layer and PU Adhesive Layer with aCrosslinker

The same procedure for the preparation of the Comparative Example 1 wasfollowed, except that the pressure sensitive adhesive solution wasreplaced with a solution containing 13.44% by weight of IROSTIC P9820-20(from Huntsman Polyurethanes), 5.6% by weight of polyisocyanate DESMODURN-100 (from Bayer) and 1% by weight of catalyst K-KAT348 (from KingIndustry) in MEK/ethyl acetate (at 92.5/7.5 ratio by weight). Thecontrast ratios of the display of Example 4 are shown in Table 1.

Example 5 Kraton Elastomer Sealing Layer and PU Adhesive Layer with aCrosslinker

The same composition and procedure for the preparation of the Example 4were followed, except that the IROSTIC P9820-20 (from HuntsmanPolyurethanes) was replaced with IROSTIC P9820-18 (from HuntsmanPolyurethanes) of the same concentration. The contrast ratios of thedisplay of Example 5 are shown in Table 1.

TABLE 1 Results of Examples 1–5 Contrast Contrast Contrast ContrastRatio (10 V) Ratio (20 V) Ratio (30 V) Ratio (40 V) Example 1 1.05 2.754.47 5.37 PSA (Comparative) Example 2 1.62 4.9 5.62 6.76 HPU-20 Example3 3.89 8.91 8.71 8.32 HPU-18 Example 4 1.45 4.17 5.5 6.76 HPU-20/DN-100/KK348 Example 5 3.39 8.71 10.47 10.23 HPU-18/DN- 100/KK348

As can be seen from Table 1, the contrast ratios of the EPD weresignificantly improved when a high dielectric polyurethane adhesive wasused as the lamination adhesive. The improvement is particularlysignificant at low operation voltages.

In addition, all the examples (2–5) using a polyurethane as thelamination adhesive showed significantly better adhesion properties thancomparative example 1 in which a pressure sensitive adhesive was used.The physicomechanical properties of the adhesive layer and in some casesthe contrast ratios may be further improved by crosslinking the adhesivelayer using a polyisocyanate crosslinking agent, DESMODUR N-100.

Examples 6–9 Microcup EPDs without a Separate Adhesive Layer

Examples 6–9 illustrate the use of a polyurethane layer as both thesealing layer and the lamination adhesive.

A. Sealing Compositions

Sealing Composition S1 (HPU-20/DN-100/KK-348):

13.44 Parts by weight of IROSTIC P9820-20 (from Huntsman Polyurethanes),79.97 parts of MEK, 6.40 parts of ethyl acetate and 0.56 parts ofDESMODUR N-100 (from Bayer) were mixed thoroughly. To the resultantsolution, 0.14 parts of K-KAT348 (from King Industry) was added. Themixture was degassed for about 1 minute in a sonic bath before use.

Sealing Composition S2 (HPU-20/polyisocyanate IE-359):

13.44 Parts by weight of IROSTIC P9820-20 (from Huntsman Polyurethanes)was thoroughly dissolved in 79.97 parts of MEK and 6.40 parts of ethylacetate, after which 0.56 parts of IRODUR E 359 (from HuntsmanPolyurethanes) was added. The resultant solution was degassed for about1 minute in a sonic bath before use.

Sealing Composition S3 (HPU-12/polyisocyanate IE-359):

The same composition and procedure for the preparation of sealingsolution S2 were followed, except that IROSTIC P9820-12 (from HuntsmanPolyurethanes) was used to replace IROSTIC P9820-20 (from HuntsmanPolyurethanes).

B. Preparation of Samples

Three test samples were prepared according to Preparations 3A–3D.However, the preparation of the samples did not involve the use of anadhesive layer.

After each of the sealing compositions, S1, S2 and S3, was overcoatedonto the filled microcups by using a 6 mil doctor blade to form asealing layer, the sealed microcups were then air-dried in a hood for 10minutes and heated in an 80° C. oven for 1 minute before lamination. Thelamination of the electrode layer over the sealed microcups wasaccomplished by laminating the ITO side of an ITO/PET film (5 mil)directly onto the sealing layer, followed by post curing at 80° C. for60 minutes and continued post curing at 65° C. overnight.

For the purpose of comparison, a control sample (Comparative Example 9)was prepared using the two layer procedure as described in Example 1. Inthe control sample, sealing composition S-1 was used to seal the filledmicrocups and the pressure sensitive adhesive (15% solution of DURO-TAK80-1105 from National Starch and Chemical Company in MEK) was used asthe adhesive layer.

C. Test Results

The contrast ratios are summarized in Table 2 in which the thickness ofthe sealing layer in the single layer system (Examples 6–8) wascontrolled to be the same as the total thickness of the sealing andadhesive layers in the two layer system (comparative Example 9).

TABLE 2 Contrast Ratios of Example 6–9 Sealing Contrast Ratio layerAdhesive 10 V 20 V 30 V 40 V 50 V Example 6 S-1 None 2.29 11.00 11.0011.20 11.20 Example 7 S-2 None 2.24 6.76 8.32 8.51 7.94 Example 8 S-3None 2.04 7.08 8.91 9.33 9.77 Comparative S-1 PSA 1.60 5.80 7.10 6.90 —Example 9

It can be seen from Table 2 that contrast ratios of EPDs sealed andlaminated with one single layer of the present invention are superiorover the control prepared from the dual layer system.

A thermoelectric module was used to control the operating temperature ofthe display for the temperature latitude study. For the measurement, thedisplay was driven at ±20V and 0.2 Hz electrical square waveform, whereincoming light from an optical fiber cable connected to a light sourcewas illuminated on the display and the reflecting light was collectedand converted into an electrical signal by a photo-electric detector andfinally the display electro-optic response was recorded. It was observedthat the single layer microcup EPDs (Examples 6–8) showed significantlywider operation temperature latitude than the two layer EPD (comparativeExample 9) using a PSA as the lamination adhesive.

Example 10

The procedure of top-sealing and lamination of Examples 6–9 wasfollowed, except that the top-sealing composition comprises 17.10 parts(dry) by weight of CAPA 6806 (received from Tri-Iso Company), 0.71 parts(dry) by weight of DESMODUR N-100 (from Bayer), and 0.17 parts by weightof catalyst K-KAT348 (from King Industry) solution was dissolved in 82parts by weight of MEK.

The sample was subjected for continuous switching under an electricfield of 1.5 volt/μm in a 50° C. and 80% relative humidity environmentalcondition. The contrast ratio of the sample was measured for each periodof time to monitor the percentage of contrast ratio changes throughoutthe whole switching period. From the test results, almost no degradationin contrast ratio was observed after 24 hours of continuously switching.

Example 11

A top-sealing composition consisting of 12.6 parts by (dry) weight ofpolyurethane IROSTIC P9815-20, 1.4 parts by weight of cellulose acetatebutyrate, CAB-551 (Eastman Chemicals Company) and 1.2% of thephotoinitiator, Irgacure 907, based on the total weight of thepolyurethane and CAB-551, was dissolved in 43 parts by weight of MEK,38.7 parts by weight of isopropyl acetate and 4.3 parts by weight ofcyclohexanone (CHO), and de-bubbled in a sonic bath for 1 minute beforeuse.

The composition was then overcoated onto the filled microcups preparedaccording to Preparation 3B, hot air blow dried for 1 minute and heatedin an 80° C. oven for 2 minutes to form a seamless sealing layer on thefilled microcup array. The top-sealed microcup array was laminateddirectly onto an ITO/PET film (5 mil) as described in Preparation 3D.

After lamination, the sample was allowed to be UV cured by passing itthrough a UV conveyer twice at the speed of 10 ft/min with intensity of2.56 W/cm² (which is equivalent to 0.856 J/cm²).

The contrast ratios of the display of Example 11 are measured and shownin Table 3.

Example 12

A top-sealing composition consisting of 12.6 parts by (dry) weight ofpolyurethane IROSTIC P9815-20, 1.4 parts by weight of polyvinyl butyrate(PVB), B-98 (received from Solutia) and 1.2% of the photoinitiator,Irgacure 907, based on the total weight of the polyurethane and PVB, wasdissolved in 86 parts by weight of MEK and de-bubbled in a sonic bathfor 1 minute before use.

The composition was then overcoated onto the filled microcups preparedaccording to Preparation 3B, hot air blow dried for 1 minute and heatedin an 80° C. oven for 2 minutes to form a seamless sealing layer on thefilled microcup array. The top-sealed microcup array was laminateddirectly onto an ITO/PET film (5 mil) as described in Preparation 3D.

After lamination, the sample was allowed to be UV cured by passing itthrough a UV conveyer twice at the speed of 10 ft/min with intensity of2.56 W/cm² (which is equivalent to 0.856 J/cm²).

The contrast ratios of the display of Example 12 are measured and shownin Table 3.

TABLE 3 Contrast Ratios of Examples 11 & 12 Contrast Ratio ContrastRatio Example # Composition (15 V) (20 V) 11 PU/CAB/Ir-907 3.63 5.13 12PU/B-98/Ir-907 3.55 4.37

While the present invention has been described with reference to thespecific embodiments thereof, it should be understood by those skilledin the art that various changes may be made and equivalents may besubstituted without departing from the true spirit and scope of theinvention. In addition, many modifications may be made to adapt aparticular situation, materials, compositions, processes, process stepor steps, to the objective, spirit and scope of the present invention.All such modifications are intended to be within the scope of the claimsappended hereto.

1. A method for improving the adhesion properties and switchingperformance of an electrophoretic display wherein display cells arefilled with an electrophoretic fluid comprising a solvent, which methodcomprises (a) applying an adhesive composition to a component of saidelectrophoretic display, or (b) sealing the filled display cells with asealing composition, wherein said adhesive or sealing compositioncomprises (i) a polymer or oligomer having a dielectric constant higherthan that of the solvent, (ii) a radically or photochemically graftablepolymer, wherein the polymer or oligomer of (i) is grafted onto thegraftable polymer of (ii), (iii) optionally a crosslinking agent, and(iv) a catalyst which is optionally present when the crosslinking agentis present.
 2. The method of claim 1 wherein said polymer or oligomer of(i) has a dielectric constant in the range of about 3.5–17 measured at18–27° C. and at 60 Hz.
 3. The method of claim 2 wherein said polymer oroligomer of (i) has a dielectric constant in the range of about 6–15measured at 18–27° C. and at 60Hz.
 4. The method of claim 1 wherein saidpolymer or oligomer of (i) is a polyurethane, polyurea, polycarbonate,polyamide, polyester, polycaprolactone, polyvinyl alcohol, polyether,polyvinyl acetate derivative, polyvinyl fluoride, polyvinylidenefluoride, polyvinyl butyral, polyvinylpyrrolidone,poly(2-ethyl2-oxazoline), high-acid-number acrylic or methacrylicpolymer or copolymer, gum Arabic, alginate, lecithin or polymer derivedfrom an amino acid.
 5. The method of claim 4 wherein said polymer oroligomer of (i) comprises a functional group for chain extension orcrosslinking.
 6. The method of claim 4 wherein said polymer or oligomerof (i) is selected from the group consisting of polyurethanes,polyureas, polycarbonates, polyesters and polyamides.
 7. The method ofclaim 6 wherein said polymer or oligomer of (i) comprises a functionalgroup selected from the group consisting of —OH, —SH, —NCO, —NCS, —NHR,—NRCONHR, —NRCSNHR, vinyl, epoxide and derivatives thereof, wherein R ishydrogen, alkyl, aryl, alkylaryl or arylalkyl.
 8. The method of claim 7wherein said polymer or oligomer of (i) is a functionalizedpolyurethane.
 9. The method of claim 8 wherein said functionalizedpolyurethane is hydroxyl terminated polyester polyurethane or polyetherpolyurethane, isocyanate terminated polyester polyurethane or polyetherpolyurethane or acrylate terminated polyester polyurethane or polyetherpolyurethane.
 10. The method of claim 9 wherein said functionalizedpolyurethane is a hydroxyl terminated polyester polyurethane.
 11. Themethod of claim 1 wherein said radically or photochemically graftablepolymer is a cellulose derivative or a polyvinyl alcohol derivative. 12.The method of claim 11 wherein said cellulose is cellulose acetatebutyrate, cellulose acetate propionate, hydroxypropyl cellulose,hydroxybutyl cellulose, hydroxyethyl cellulose, methyl cellulose,carboxymethyl cellulose, or a copolymer thereof.
 13. The method of claim11 wherein said polyvinyl alcohol derivative is polyvinyl acetal,polyvinyl butyral, or a copolymer thereof.
 14. The method of claim 1wherein said radically or photochemically graftable polymer is celluloseacetate, cellulose acetate butyrate, cellulose acetate propionate,polyvinyl acetal or a copolymer thereof.
 15. The method of claim 1wherein said radically or photochemically graftable polymer is presentin an amount of about 5% to about 30% by weight of the polymer oroligomer of (i).
 16. The method of claim 15 wherein said radically orphotochemically graftable polymer is present in an amount of about 10%to about 20% by weight of the polymer or oligomer of (i).
 17. The methodof claim 1 wherein said adhesive or sealing composition furthercomprises a photoinitiator.
 18. The method of claim 17 wherein saidphotoinitiator is benzophenone, isopropyl thioxanthone,4(p-tolylthio)benzophenone, 2,2-dimethoxy- 1,2-diphenylethane,2-methyl-1-[4-(methylthio)phenyl]-2-morpholino-1-propanone,2-benzyl-2-(dimethylamino)-1-[4-(4-morpholinyl)phenyl]-1-butanone or 1-hydroxycyclohexylphenylketone.
 19. The method of claim 17 wherein saidphotoinitiator is present in an amount of about 0.5% to about 5% byweight based on the total weight of the polymer or oligomer of(i) andthe radically or photochemically graftable polymer.
 20. The method ofclaim 19 wherein said photoinitiator is present in an amount of about 1%to about 3% by weight based on the total weight of the polymer oroligomer of (i) and the radically or photochemically graftable polymer.21. The method of claim 1 wherein said crosslinking agent is amultifunctional isocyanate.
 22. The method of claim 21 wherein saidmultifunctional isocyanate is an aliphatic polyisocyanate.
 23. Themethod of claim 1 wherein said catalyst is selected from the groupconsisting of organotin catalysts, organozirconium catalysts and bismuthcatalysts.
 24. The method of claim 23 wherein said organotin catalyst isdibutyltin dilaurate.
 25. The method of claim 1 wherein saidelectrophoretic display is prepared using the microcup technology.